Which of the following are examples of physical change? dew forms on a blade of grass a halloween light stick glows after shaking an egg solidifies during cooking a hydrogen balloon explodes when contacted with a flame none of the above are physical changes.

a) Dew forms on the blade of grass

Explanation:

The only example of physical change in given options is

a) Dew forms on the blade of grass

water is there in the atmosphere in vapor form, and it comes contact with cooler grass ( colder air has less capacity to hold water than the warmer air), it condenses.

b) halloween light stick glows after shaking is a chemical change and so are soldification of egg on cooking and explosion of hydrogen balloon.

dew forms on a blade of grass

Explanation:

A change that does not bring any difference in chemical composition of a substance are known as physical properties.

For example, shape, size, mass, volume, density, etc of a substance are all physical change.

And, a change in which there occurs a difference in chemical composition of a substance then it is known as chemical change.

For example, precipitation, reactivity, toxicity etc are chemical change.

Out of the given options:-  dew forms on a blade of grass is a physical change as their is change in the state of the matter.

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.