Science in Everyday Life

Term 1 Chapter 4 | 3rd Science

Questions with Answers, Solution, and Evaluation

EVALUATION

I. Say whether the following statements are true or false.

1. When we boil water, bacteria are destroyed. (True)

2. Idli is cooked by the process called steaming. (True)

3. Thermometer is used to measure pressure. (False)

4. Refrigerator helps to keep things cold. (True)

5. Garlic relieves hiccups and nausea. (False)

6. Boiling point of water is 100°C. (True)

II. Circle/underline the name of the things from which idli is made.

Rice Groundnut Chilli Black gram Red gram Water Salt Pepper Sugar Fenugreek

III. Match the home appliances and their functions.

Analyze the images below and match the appliance to its correct usage.

IV. Which of these are safe to do at home? Put (✔) or cross (×) in the box.

1. Touching electrical appliances (×)

2. Playing with sharp objects (×)

3. Playing in kitchen (×)

4. Keep safe distance from the gas stove and cylinder (✔)

V. Answer in a word or sentence.

1. How do you store fruits and vegetables for a longer period? We stone fruits and vegetables for a longer time by preserving them in a refrigerator.

2. Name the instrument used to measure temperature. Thermometer is used to measure temperature.

3. How is idli prepared? Idli is prepared by the method called steaming.

4. What is the use of black pepper? Black pepper is a great remedy for cold and cough.

5. Which kitchen medicine is called the poor man‛s antibiotic? Garlic is called the poor man's antibiotic.

VI. Answer the following.

1. Write the uses of boiled water.

Uses of boiled water:

(i) Destroys germs.

(ii) Improves digestion.

(iii) Prevents us from the infection of water borne diseases.

2. Write the advantages of pressure cooker.

Advantages of pressure cooker:

(i) Saves time.

(ii) Minimizes the usage of fuels and saves energy.

(iii) Retains nutrients in food.

(iv) Preserves the appearance of food.

3. The doctor advices patients to have idli or idiyappam. Can you guess why?

(i) Idli is cooked by steaming.

(ii) Steamed food is easily digested.

Tick (✓) the item which you see in your kitchen.

Tick (✓) the food items which are made by steaming.

Arrange the pictures in correct order.

Let us Discuss

1. Which one takes less time to cook pulses?
a. pressure cooker b. mud pot

Answer : a. pressure cooker

2. List out the food items prepared by using pressure cooker. Discuss with your friends.

Pulses, Rice, Idli, Briyani.

Match Column A with Column B.

Match the related items in the images below.

What are your favourite food items? Do you know the ingredients of them? Do they have any medicinal value? If so, fill in the table.

My favourite food: Gooseberry juice

Ingredients:

Gooseberry

Ginger

Jaggery

Medicinal value:

Vitamin C

Improves digestion

For what ?

To learn how the shadows are formed.

How?

1. Make the classroom dark.

2. Light a candle.

3. Place a toy near the candle. What do you see?

4. Move the toy away from the candle. What do you see? Move the toy closer to the candle. What do you look at?

5. Experiment and see what happens to the shadow if the light source is dim?

Complete the sentence:

* Moving the toy closer to the candle made its shadow Short.

* While moving the object away made its shadow Long.

* The big candle is bright and gives dark, clear shadow.

* The small is dim and gives dim shadow.

Lava in a Cup

You will Need: A tall glass cup, 1/4 cup vegetable oil, 1 teaspoon salt, water, food colour.

What to do?

1. Fill the glass about 3/4 with water.

2. Add about 5 drops of food colour (Red).

3. Slowly pour the vegetable oil into the glass. See how the oil floats on top.

4. Sprinkle the salt on top of the oil.

5. Watch blobs of lava move up and down in your glass! Add another teaspoon of salt to keep the effect going.

What happens when you

add oil to water?
Oil floats in water.

add colour to the mix?
It becomes coloured.

add salt to the mix?
Coloured oil bubbles rises up and goes down.

First of all, the oil floats on the top of the water because it is lighter than the water. Since the salt is heavier than oil, it sinks down into the water and takes some oil with it, but when the salt dissolves, the oil goes up again. Is it not interesting?

Let us measure the boiling point of water using thermometer

Boiling point of water is 100°C

Things Needed : Water and thermometer

Procedure :
Heat the water. Measure the initial temperature, when the water starts to boil. Allow it to boil for few more minutes, measure the temperature.
The temperature remains the same when the boiling point reaches 100°C and continues to boil for some more time.

Similarly, the boiling point of milk can also be measured using thermometer.

Colour the thermometer to match the temperature written in the box.

The Physics of a Spanner: Understanding Torque

Ever wondered why it's easier to loosen a stubborn nut with a longer wrench? The answer isn't magic; it's physics! Specifically, it's a fundamental concept called torque, or the moment of force.

Torque is the measure of the force that can cause an object to rotate around an axis. Think of it as a "turning" or "twisting" force. It’s at play in many of our daily activities, from pushing open a door (you push farthest from the hinges, right?) to pedaling a bicycle.

To see this principle in action, let's break down a classic physics problem.

The Problem

A mechanic unscrews a nut by applying a force of 140 Newtons (N) with a spanner that is 40 centimeters (cm) long.

Question: What should be the length of the spanner if a force of only 40 N is applied to unscrew the exact same nut?

The Science Behind the Solution

To loosen the nut, a specific amount of torque is required. This required torque is a constant. It doesn't change whether you use a short spanner with a lot of force or a long spanner with less force. The turning effect must be the same.

The formula for torque is simple:

$$Torque = Force \times \text{Perpendicular Distance from the pivot}$$

In our case, the "distance" is the length of the spanner. Let's call our first scenario (Case 1) and our second scenario (Case 2). The core principle is:

$$Torque_1 = Torque_2$$

Which means:

$$(Force_1 \times \text{Length}_1) = (Force_2 \times \text{Length}_2)$$

Solving the Problem Step-by-Step

Let's list what we know:

Force 1 ($F_1$): 140 N
Length 1 ($d_1$): 40 cm
Force 2 ($F_2$): 40 N
Length 2 ($d_2$): ? (This is what we need to find)

Now, we plug these values into our equation:

$$F_1 \times d_1 = F_2 \times d_2$$

$$140 \text{ N} \times 40 \text{ cm} = 40 \text{ N} \times d_2$$

To solve for $d_2$, we can rearrange the equation:

$$d_2 = \frac{(140 \text{ N} \times 40 \text{ cm})}{40 \text{ N}}$$

As you can see, the "40 N" on the top and bottom of the fraction cancel each other out.

$$d_2 = 140 \text{ cm}$$

Answer: The mechanic would need a spanner that is 140 cm long.

The Takeaway

This problem beautifully illustrates the inverse relationship between force and the length of the lever arm when torque is constant.

Less force? You need a longer lever.
Shorter lever? You need to apply more force.

So, the next time you're struggling with a tight bolt, remember your physics lesson and grab a longer wrench!

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